Regex

<?php
const PATTERN_RFC3986 = '~^
      (?<scheme>[a-z][a-z0-9+-\.]*)
      ://
        (?:
          (?<userinfo>
           ([a-z0-9\-\._\~!\$&\'()*+,;=:]|%[0-9a-f]{2})*
          )@ # *( unreserved / pct-encoded / sub-delims / ":" )
        )?

        (?<host>
          (?<ipv4>
            (?<ipv4Dec>25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)
            (?:\.(?P>ipv4Dec)){3}
          ) # a IPv4 address
          |
          (?<ipv6>
            \[
            (?:
              (?:
                (?<ipv6h16>[0-9a-f]{1,4}):(?:(?P>ipv6h16):){5}
                (?<ipv6ls32>
                  (?:(?P>ipv6h16):(?P>ipv6h16))
                  |
                  (?<ipv6ipv4>
                    (?<ipv6ipv4Dec>25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)
                    (?:\.(?P>ipv6ipv4Dec)){3}
                  )
                )
              ) # 6( h16 ":" ) ls32
              |
              (?:::(?:(?P>ipv6h16):){5}(?P>ipv6ls32)) # "::" 5( h16 ":" ) ls32
              |
              (?:(?P>ipv6h16)?::(?:(?P>ipv6h16):){4}(?P>ipv6ls32)) # [ h16 ] "::" 4( h16 ":" ) ls32
              |
              (?:(?:(?:(?P>ipv6h16):){1,2}|:):(?:(?P>ipv6h16):){3}(?P>ipv6ls32)) # [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32
              |
              (?:(?:(?:(?P>ipv6h16):){1,3}|:):(?:(?P>ipv6h16):){2}(?P>ipv6ls32)) # [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32
              |
              (?:(?:(?:(?P>ipv6h16):){1,4}|:):(?P>ipv6h16):(?P>ipv6ls32)) # [ *3( h16 ":" ) h16 ] "::" h16 ":" ls32
              |
              (?:(?:(?:(?P>ipv6h16):){1,5}|:):(?P>ipv6ls32)) # [ *4( h16 ":" ) h16 ] "::" ls32
              |
              (?:(?:(?:(?P>ipv6h16):){1,6}|:):(?P>ipv6h16)) # [ *5( h16 ":" ) h16 ] "::" h16
              |
              (?:(?:(?:(?P>ipv6h16):){1,7}|:):) # [ *6( h16 ":" ) h16 ] "::"
            )
            \]
          ) # a IPv6 address
          |
          (?<ipvfuture>
            \[
              v[0-9a-f]+ \. [a-z0-9\-\._\~!\$&\'()*+,;=:]+ # "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" )
            \]
          ) # a future IP address
          |
          (?<regname>
             ([a-z0-9\-\._\~!\$&\'()*+,;=]|%[0-9a-f]{2})* # *( unreserved / pct-encoded / sub-delims )
          ) # a registered name
        )

        (?:
          :(?<port>[0-9]*)
        )?

        (?<pathabempty>
          (?:
            /(?<segment>([a-z0-9\-\._\~!\$&\'()*+,;=:@]|%[0-9a-f]{2})*) # *pchar
          )*
        ) # *( "/" segment )

        (?:
          \?
          (?<query>
            ([a-z0-9\-\._\~!\$&\'()*+,;=:@/?]|%[0-9a-f]{2})*
          ) # *( pchar / "/" / "?" )
        )?

        (?:
          \#
          (?<fragment>
            ([a-z0-9\-\._\~!\$&\'()*+,;=:@/?]|%[0-9a-f]{2})*
          ) # *( pchar / "/" / "?" )
        )?
    $~ixu'